Can't append json array into a json array in postgresql function - arrays

Question

I am trying to append a json array or object into a json array but array_append always inserts the json as string.
My result is;
{"{"category_id":8,"category_name":"08 Candy","is_active":true,"category_name_app":"Candy","display_order":7}"}
but i want it to be like this. So i can json_decode them in my code.
[{"category_id":8,"category_name":"08 Candy","is_active":true,"category_name_app":"Candy","display_order":7}]
here is my function logic
for all_categories in select * from categories where is_active = '1' loop
show_at_homepage = 0;
for current_subcat in select * from public."V_category_to_sub_category_w_names" where category_id = all_categories.category_id and sub_category_is_active = '1' loop
select * into product_count from public."V_APP_products_w_sub_categories" where sub_category_id = current_subcat.sub_category_id and store_id = get_store_id and is_deleted='0';
if count(product_count) > 0 then
show_at_homepage = 1;
end if;
end loop;
if show_at_homepage = 1 then
select row_to_json(all_categories) into cat_json;
select array_append(my_json_result_array,cat_json) into my_json_result_array;
end if;
end loop;
return my_json_result_array;

Answer 1

You can apply array_append to any kind of array of postgres data types, including json[], but you can't apply it to a json array which is of type json. In your case, you need to apply the json functions and operators, see the manual, and more specifically the json_build_array function :
Replace
select array_append(my_json_result_array,cat_json) into my_json_result_array
By
select json_build_array(my_json_result_array,cat_json) into my_json_result_array
Or when you use jsonb instead of json which is the manual recommendation :
select jsonb_build_array(my_json_result_array,cat_json) into my_json_result_array